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IDT
Notes
PES4T4 User Manual
To define buses, the most significant bit (MSB) will be on the left and least significant bit (LSB) will be on
the right. No leading zeros will be included.
Throughout this manual, when describing signal transitions, the following terminology is used. Rising
edge indicates a low-to-high (0 to 1) transition. Falling edge indicates a high-to-low (1 to 0) transition. These
terms are illustrated in Figure 1.
single clock cycle
1
high-to-low
transition
Numeric Representations
To represent numerical values, either decimal, binary, or hexadecimal formats will be used. The binary
format is as follows: 0bDDD, where "D" represents either 0 or 1; the hexadecimal format is as follows:
0xDD, where "D" represents the hexadecimal digit(s); otherwise, it is decimal.
The compressed notation ABC[x|y|z]D refers to ABCxD, ABCyD, and ABCzD.
The compressed notation ABC[x:y]D refers to ABCxD, ABC(x+1)D, ABC(x+2)D,... ABCyD if x < y or to
ABCxD, ABC(x-1)D, ABC(x-2)D,... ABCyD if x > y.
Data Units
The following data unit terminology is used in this document.
Term
Byte
Word
Doubleword (Dword)
Quadword (Qword)
In quadwords, bit 63 is always the most significant bit and bit 0 is the least significant bit. In double-
words, bit 31 is always the most significant bit and bit 0 is the least significant bit. In words, bit 15 is always
the most significant bit and bit 0 is the least significant bit. In bytes, bit 7 is always the most significant bit
and bit 0 is the least significant bit.
The ordering of bytes within words is referred to as either "big endian" or "little endian." Big endian
systems label byte zero as the most significant (leftmost) byte of a word. Little endian systems label byte
zero as the least significant (rightmost) byte of a word.
2
3
low-to-high
transition
Figure 1 Signal Transitions
Words
Bytes
1/2
1
1
2
2
4
4
8
Table 1 Data Unit Terminology
2
4
Bits
8
16
32
64
February 1, 2011
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